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Biomedical subjects

Atsushi Uchida

Publications and source records attributed to Atsushi Uchida.

17 recordsLinked to original sources
PubMed2006

Synchronization of unidirectionally coupled Mackey-Glass analog circuits with frequency bandwidth limitations.

Synchronization of chaotic systems has been studied extensively, and especially, the possible applications to the communication systems motivated many research areas. We demonstrate the effect of the frequency bandwidth limitations in the communication channel on the synchronization of two unidirectionally coupled Mackey-Glass (MG) analog circuits, both numerically and experimentally. MG system is known to generate high dimensional chaotic signals. The chaotic signal generated from the drive MG system is modified by a low pass filter and is then transmitted to the response MG system. Our results show that the inclusion of the dominant frequency component of the original drive signals is crucial to achieve synchronization between the drive and response circuits. The maximum cross correlation and the corresponding time shift reveal that the frequency-dependent coupling introduced by the low pass filtering effect in the communication channel change the quality of synchronization.

Journal Article↗
PubMed2006

Gastrointestinal oxalic acid absorption in calcium-treated rats.

We studied whether urinary oxalate excretion after an acute oral load of oxalic acid is influenced by concomitant administration of calcium in rats. Male Wistar rats weighing approximately 180 g were divided into six groups of five animals each. After inducing anesthesia, the animals were orally (via a gastrostomy) given 110 micromol of oxalic acid along with 0, 27.5, 55, 110, or 220 micromol of calcium (0, 27.5, 55, 110, or 220 micromol Ca group, respectively). Saline was given to the control group instead of oxalic acid. Urine specimens were collected before administration and then at hourly intervals up to 5 h afterward. Urinary oxalate and citrate levels were measured by capillary electrophoresis, while urinary calcium, magnesium, and phosphorus levels were measured by ICP spectrophotometry. Urinary oxalate excretion peaked at 1 h after administration and was higher in the 0, 27.5, and 55 micromol Ca groups than in the control group. The urinary recovery of oxalate in these groups was 10-15%, while the recovery rate was less than 3% in other groups. Urinary Ca excretion showed no significant changes, either over time or between groups. Free oxalic acid is absorbed more readily from the gastrointestinal tract than calcium oxalate, while simultaneous administration of calcium appears to block intestinal oxalic acid absorption in a dose-dependent manner.

Animals↗
PubMed2006

Calcium oxalate saturation in dialysis patients with and without primary hyperoxaluria.

Calcium oxalate supersaturation of the blood is associated with deposition of crystals in various tissues. We measured the serum levels of oxalate, citrate, calcium, and magnesium to estimate their saturation in 112 hemodialysis patients without primary hyperoxaluria and two boys with primary hyperoxaluria. Serum levels of oxalate and citrate were determined by high-performance capillary electrophoresis, while calcium and magnesium were measured by ICP spectroscopy. The serum levels of oxalate, citrate, calcium, and magnesium were 44.9+/-16.5, 138.1+/-54.9 micromol/l, 2.30+/-0.28, and 1.07+/-0.18 mmol/l, respectively, while the levels in patients with primary hyperoxaluria were 83.9+/-34.3, 197.9+/-63.5 micromol/l, 2.53+/-0.15, and 1.14+/-0.34 mmol/l, respectively. Serum calcium oxalate saturation (SS), as calculated by the Equil program, was significantly correlated with the serum oxalate level. Most patients showed metastable supersaturation (1<SS<8.9), which was associated with a serum oxalate level of more than 30 micromol/l. Serum saturation exceeded the formation product (SS=8.9) in some specimens from patients with type 1 primary hyperoxaluria. The serum calcium oxalate saturation [SS(CaOx)] showed a significant positive correlation with the levels of oxalate [Ox], calcium [Ca], and citrate [Cit]: [SS(CaOx)]=-0.3562+34.634[Ox]+0.394[Ca]-0.483[Mg]+0.101[Cit], (all mmol/l, r=0.9848, P<0.01). This formula is useful for estimating the saturation. In conclusion, the serum oxalate level is a good indicator of calcium oxalate saturation and should be monitored accurately while keeping it lower in dialysis patients.

Aged↗
PubMed2006

Retroperitoneoscopic partial nephrectomy using radiofrequency ablation.

Two patients with renal tumors underwent retroperitoneoscopic partial nephrectomy. The renal tumors were initially treated with radiofrequency ablation. This method allowed tumor excision to be achieved without clamping the renal pedicle. Residual renal function was well maintained as determined by enhanced computed tomography scanning and measurement of the serum creatinine level. There were no complications such as vascular damage or collecting system injury. The pathological diagnosis was clear cell carcinoma (pT1) in Patient 1 and was not determined in Patient 2 because of entire ablation. No recurrence has been observed after 3 years and 2 years of follow up, respectively. Radiofrequency ablation was useful for control of local bleeding during retroperitonaoscopic partial nephrectomy.

Adenocarcinoma, Clear Cell↗
PubMed2006

Mucoid pseudocyst of the obturator nerve.

A 71-year-old man visited the outpatients' clinic of National Saitama Hospital, Japan, complaining of pain in the right leg. Magnetic resonance imaging (MRI) revealed a cystic mass adjacent to the right side of the urinary bladder. He underwent the removal of the cystic mass and the pathological diagnosis was a mucoid pseudocyst of the obturator nerve. After tumor resection, the pain was diminished and he has been free of disease for 3 years.

Aged↗
PubMed2006

Effect of vitamin B6 deficiency on glyoxylate metabolism in rats with or without glyoxylate overload.

We examined the effect of vitamin B6 deficiency on glyoxylate metabolism and hepatic alanine: glyoxylate aminotransferase (AGT) activity in rats with normal or high glyoxylate intake. Male rats were divided into four groups: a control group, a vitamin B6-free diet group, a glyoxylate water group, and a vitamin B6-free diet + glyoxylate water group. Each group was given special diet (control or vitamin B6-deficient diet) and drinking water (plain or 0.5% glyoxylate water) for 4 weeks, after which biochemical parameters and hepatic AGT mRNA level were measured. Compared with control rats, the urinary oxalate/creatinine ratio was higher in each of the other 3 groups. The urinary glycolate/creatinine ratio was also higher in the vitamin B6-free diet group and the vitamin B6-free diet + glyoxylate water group than the control group, while the urinary glycine/creatinine and citrate/creatinine ratio was lower in both groups. The hepatic AGT mRNA level was reduced in the vitamin B6-free diet group, but was increased in the glyoxylate water group than the control group. These results suggest that vitamin B6 is necessary for glyoxylate metabolism as a coenzyme of AGT. Especially in the presence of a high glyoxylate intake, vitamin B6 deficiency leads to severe hyperoxaluria and hypocituria.

Alanine↗
PubMed2005

Expression of myelencephalon-specific protease after cryogenic lesioning of the rat parietal cortex.

The gene for myelencephalon-specific protease (MSP) is a member of the kallikrein gene family and in rats is expressed mainly in the central nervous system. Its function and alteration in brain injury have not yet been clarified. We examined the expression of MSP after cryogenic injury (CI) using in situ hybridization, immunohistochemistry, and Western blotting. Analysis of MSP mRNA by in situ hybridization revealed a higher level of expression around the cryogenic area than on the contralateral side at 2-7 days after CI, with peak expression occurring 7 days after CI. Immunohistochemical analysis demonstrated expression of MSP protein at 1 day after CI, in the same region in which MSP mRNA was observed, with peak expression again at 7 days after CI, in the area around the lesion. Double immunohistochemical labeling revealed that MSP was expressed mainly in oligodendrocytes. These results suggest that expression of MSP may be related to the turnover of myelin-associated proteins and extracellular matrix proteins after CI. The regulation of active MSP may be important in the physiological or pathological changes involved in remyelination or demyelination.

Animals↗
PubMed2005

Urinary response to an oxalic acid load is influenced by the timing of calcium loading in rats.

PURPOSE: Dietary intake of calcium or dairy products has been shown to decrease urinary oxalate excretion by limiting its intestinal absorption. However, not enough attention has been given to whether there is any benefit from altering the schedule of ingesting calcium and oxalate. Therefore, we investigated the effects of changes in the timing of calcium and oxalate loading on urinary oxalate excretion. MATERIALS AND METHODS: Male Wistar rats weighing 180 to 200 gm were fasted and randomized into several groups. They were then administered normal saline or oxalic acid with or without calcium or milk. Calcium or milk was given immediately, or 5, 10, 15 or 30 minutes before or after the oxalate load. All treatments were given via gastrostomy. Urine samples were collected by bladder puncture just before administration and at hourly intervals up to 5 hours afterward. Urinary oxalate was measured by capillary electrophoresis. RESULTS: Urinary oxalate increased after the administration of oxalate alone, while it decreased when oxalate was combined with calcium or milk. Urinary oxalate showed a smaller increment when calcium or milk was given before than after oxalate loading, and it was much smaller when calcium or milk was given immediately before oxalate. CONCLUSIONS: Prior calcium loading appears to have a positive influence on decreasing oxalic acid absorption from the intestinal tract. Therefore, calcium or dairy products should always be ingested before a meal rich in oxalate to prevent oxalate absorption and decrease urinary oxalate excretion.

Analysis of Variance↗
PubMed2004

Consistency of nonlinear system response to complex drive signals.

The consistency of a nonlinear system's response to a repeated complex waveform drive signal is an important consideration in classical and quantum systems as diverse as lasers, neuronal networks, and manufacturing plants. We show from a consideration of different characteristic waveforms that there is typically an optimal drive amplitude for the most consistent response; internal noise sources dominate for small amplitude driving while deterministic system nonlinearity reduces consistency for large amplitudes. We test this general concept and its measurement experimentally and numerically on the specific example of a laser system.

Algorithms↗
PubMed2004

Chaotic wavelength division multiplexing for optical communication.

We demonstrate wavelength division multiplexing with chaotic subcarriers in two pairs of one-way-coupled Nd:YVO4 microchip lasers. Two individual digital messages are encoded on two chaotic carriers with different wavelengths in two transmitters by the chaotic masking method, and the mixed signals are sent to two receivers. Dual synchronization of chaos is used to obtain the original chaotic waveforms in the receivers. Two messages are decoded by filtering the difference of the laser outputs between the transmitter and the receiver by use of a low-pass filter for each pair of lasers. The message recovery can be achieved more easily when messages with small amplitude and low frequency are used.

Journal Article↗
PubMed2004

Expression of myelencephalon-specific protease in transient middle cerebral artery occlusion model of rat brain.

Myelencephalon-specific protease (MSP) is one of the serine proteases and is expressed in the central nervous system of rats. Its function and alternation in brain injury have not yet been clarified. In this study, we investigated the expression of MSP after transient middle cerebral artery occlusion (MCAO) using in situ hybridization and immunohistochemistry. In situ localization of MSP mRNA demonstrated a higher level in the corpus callosum and around the ischemic area from 12 h to 14 days after MCA reperfusion, with the peak of expression coming 3 days after reperfusion in both regions. Immunohistochemically, the expression of protein was found 1 day after reperfusion in the same brain region that was observed for mRNA. The peak was 7 days after reperfusion in both regions. Micro-autoradiography, immunostaining and double immunohistochemical labeling revealed the expression of MSP to be located mainly in the oligodendrocytes. The present results indicate that MSP may be related to the turnover of the myelin-associated proteins and the extracellular matrix proteins after transient MCAO. The activation of MSP may play a role in remodeling processes such as neurite outgrowth and remyelination.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed2004

[Advanced renal cell carcinoma showing a different response to two types of interferon-alpha].

Interferon (IFN)-alpha has been widely used in systemic therapy for advanced renal cell carcinoma (RCC). IFN-alpha is represented by a large family of structurally related genes expressing at least 14 subtypes, each of which shows quantitatively distinct patterns of biological activities. Although those distinct patterns of biological activities of IFN-alpha subtypes against renal cancer cell lines have been demonstrated, there is no report that demonstrates the difference in each subtype-induced antitumor activity in patients with RCC. Herein, we present a unique case of advanced RCC that is resistant to interleukin-2 and IFN-alpha administration, and we describe its response to another IFN-alpha administration. The difference between the two IFN-alpha types lies in the distribution of the subtypes: this case, therefore, suggests that the difference in the subtype distribution may cause the different response of the RCC. A 47 year-old male was diagnosed as left RCC with multiple lung metastases and underwent radical nephrectomy. The histological diagnosis was pT3b G2 clear cell carcinoma. He received intramuscular administration of 6 x 10(6) units of natural human IFN-alpha (Sumiferon) three times a week following the operation. However, the lung metastases showed progression. Thereafter, he received intravenous administration of 1.4 x 10(6) units of human interleukin-2 everyday. However, the lung metastases showed further progression and the hemoptysis, dyspnea, and chest pain deteriorated. Finally, he was given intramuscular administration of 5 x 10(6) units of another natural human IFN-alpha (OIF) three times a week. After the OIF administration, his complaints subsided and a chest CT scan revealed reduced lung metastases and diminished pleural effusion. He had not received any anti-tumor agents other than IFN-alpha or interleukin-2 since the operation. However, although he remained free of hemoptysis, dyspnea, and chest pain after OIF administration, the lung metastases increased again and multiple brain metastases were also observed five months after the first OIF administration. He died of metastatic RCC one year after the operation.

Antineoplastic Agents↗
PubMed2003

Generalized synchronization of chaos in identical systems with hidden degrees of freedom.

We demonstrate generalized synchronization of chaos in a two-mode laser system. The total intensity of the laser output (the sum of the individual mode intensities) is used as the drive signal. This lumped variable transmitted to the identical response system does not generate identical synchronization. Generalized synchronization is observed instead of identical synchronization because of the hidden internal degrees of freedom.

Feedback↗
PubMed2003

Elevated Akt activation and its impact on clinicopathological features of renal cell carcinoma.

PURPOSE: Akt has been implicated in the pathogenesis and progression of numerous human malignant tumors because Akt regulates many key effector molecules involved in controlling the balance of survival and apoptosis. Elevated Akt activation has been demonstrated in various types of malignant tumors. In the current study we evaluated Akt activation in renal cell carcinoma and investigated its association with pathological features and clinical outcome. MATERIALS AND METHODS: Akt activation was evaluated by immunohistochemistry using antiphospho-specific Akt antibody, which recognizes only activated Akt, in 48 patients with renal cell carcinoma. High immunostaining tumors were defined as tumors with increased staining intensity compared with adjacent nonneoplastic kidney tissue and low immunostaining tumors were defined as tumors with equivalent or decreased staining intensity. The association of Akt activation status with clinicopathological features was analyzed. RESULTS: Of 48 patients examined 18 (37.5%) demonstrated high antiphospho-specific Akt immunostaining compared with adjacent nonneoplastic kidney tissue, while 30 (62.5%) demonstrated low immunostaining. Elevated immunostaining was significantly associated with tumor grade (p = 0.0354) and metastatic disease (p = 0.0044), while it was not associated with tumor stage or histological subtype. In addition, high antiphospho-specific Akt immunostaining was significantly associated with a poor cancer specific survival rate on univariate analysis (p = 0.0109) but not on multivariate analysis. CONCLUSIONS: Elevated Akt activation could be a common finding, especially in high grade tumor and metastatic disease. It could have an important role in the pathogenesis and progression of renal cell carcinoma.

Adult↗
PubMed2002

Activation of signal transducer and activator of transcription 3 in renal cell carcinoma: a study of incidence and its association with pathological features and clinical outcome.

PURPOSE: Signal transducer and activator of transcription 3 (STAT3) is known to have an important role in cytokine and growth factor signaling pathways. In various types of human malignant tumors STAT3 has been shown to be constitutively activated due to aberrant production of cytokines and growth factors. We examined the presence of STAT3 activation and its association with pathological features and clinical outcome in renal cell carcinoma cases. MATERIALS AND METHODS: We examined 48 paraffin embedded renal cell carcinoma specimens and corresponding nonneoplastic kidney tissues for the activation status of STAT3 on immunohistochemistry using anti-phospho-specific (p)-STAT3 antibody, which recognizes only activated STAT3. Based on the percent of cells with positive nuclear staining the activation status of STAT3 was determined and categorized into 2 groups, including low-less than 10% and high-90% or more tumor cells positive. The associations of the activation status of STAT3 with pathological features and clinical outcome were analyzed. RESULTS: Of 48 tumors 24 (50%) demonstrated high levels of nuclear immunostaining for p-STAT3, while the other 24 (50%) showed low levels. Adjacent nonneoplastic kidney tissues showed only little immunostaining for p-STAT3. A significant association of high levels of p-STAT3 with metastasis was observed (p = 0.0094). No significant associations of p-STAT3 immunostaining with pathological stage or grade were observed. A high level of p-STAT3 was a significant indicator of a poor prognosis on univariate and multivariate analysis (p = 0.0117 and 0.0439, respectively) CONCLUSIONS: Our results indicate a high frequency of STAT3 activation in renal cell carcinoma, especially in metastatic disease. STAT3 activation was an independent prognostic variable in renal cell carcinoma cases. Our results strongly suggest that the activation of STAT3 contributes to the development and progression of renal cell carcinoma.

Acute-Phase Proteins↗